Method for operating an internal combustion engine

ABSTRACT

In a method for operating an internal combustion engine comprising at least one a cylinder with a combustion chamber, wherein by means of at least one detection device assigned to the combustion chamber a first value characterizing the pressure in the combustion chamber is detected, wherein on the basis of the first value at least a second value characterizing a progression of the energy released during a combustion in the combustion chamber is determined, on the basis of the second value at least a third value is determined, by means of which the progression of the combustion is subdivided into at least two sub-curves and one of the sub-curves is assigned to a normal combustion for operation of the internal combustion engine and the other of the sub-curves is assigned to a special combustion differing from the normal combustion.

This is a Continuation-In-Part application of pending international patent application PCT/EP2010/005639 filed Sep. 14, 2010 and claiming the priority of German patent application 10 2009 057 662.2 filed Sep. 14, 2009.

BACKGROUND OF THE INVENTION

The invention relates to a method for operating an internal combustion engine having a combustion chamber including a detection device for determining the pressure in the combustion chamber during combustion.

Such a method is basically known from DE 10 2004 033 072 A1. This document discloses a method for controlling an internal combustion engine, wherein a first value is detected with at least one sensor which characterizes the pressure in the combustion chamber of at least one cylinder of the internal combustion engine, and then, on the basis of the first value, a second value is determined which characterizes the energy released during the combustion. If a threshold of the second value is exceeded a third value characterizing the combustion process is established.

EP 1 936 156 A1 discloses a method which detects the pressure value in the combustion chamber of a cylinder of an internal combustion engine in order to control the internal combustion engine, wherein on the basis of this first value a second value is determined which characterizes the energy released during combustion. The progression of the combustion of individual fuel injections is respectively characterized within fixedly applied time windows by means of further values.

The known methods however have further potential for optimizing the operation of an internal combustion engine.

It is thus the principal object of the present invention to provide a method for operating an internal combustion engine of the type mentioned above which facilitates an improved and simple operation of the internal combustion engine.

SUMMARY OF THE INVENTION

In a method for operating an internal combustion engine comprising at least one cylinder with a combustion chamber, wherein by means of at least one detection device assigned to the combustion chamber a first value characterizing the pressure in the combustion chamber is detected, wherein on the basis of the first value at least a second value characterizing a progression of the energy released during a combustion in the combustion chamber is determined, on the basis of the second value at least a third value is determined, by means of which the progression of the combustion is subdivided into at least two sub-curves and one of the sub-curves is assigned to a normal combustion for operation of the internal combustion engine and the other of the sub-curves is assigned to a special combustion differing from the normal combustion.

The method according to the invention thus allows to obtain with the use of a single detection device specific to the combustion chamber, for example a pressure sensor, different combustion characteristics which are also described as combustion features from a detected pressure signal of the operating chamber. Furthermore the method according to the invention allows, through the determination of at least one such combustion feature, advantageously through the determination of different combustion features dependent upon the engine operating state, and their incorporation into a control circuit, a control of the combustion to be carried out, in particular in special operating states, wherein in these special operating states for example a special combustion is carried out in addition to the normal combustion for the operation of the internal combustion engine, in order for example to regenerate an exhaust gas purification device such as for example a particle filter. In addition it allows a particularly good and efficient transition between operating states in which for example a regeneration or similar are carried out and operating states in which such a special combustion is not carried out.

All this is made possible through the use of the detection device, which is present anyway for detecting the value characterizing the pressure in the combustion chamber, without the need for an additional sensor system or additional detection devices. Also, no additional correction functions and characteristic fields are necessary.

On the one hand this improves the control procedure for operating the internal combustion engine in particular in the previously mentioned special operating states which to appropriately control has not been possible thus far. On the other hand this keeps necessary data input and application resources within limits, which results in lower costs for the method according to the invention and for the operation of the internal combustion engine at low power levels.

By determining the at least one combustion feature, thus the third value, by means of which the progression of the combustion is divided into at least two sub-curves and whereby therefore the possibility is created in the progression of the combustion to not only characterize the normal combustion but instead also the special combustion in special operating states, it is possible by means of a multi-value regulation to optimally control the progression of the combustion in those operating states in association with a common structure.

In case of such special operating states it is a question of said particle filter regeneration, wherein the particle filter is for example a diesel particle filter, or a question of a DeNOx and/or DeSOx combustion process, cold start modes, hot combustion processes or similar.

The second value is for example an integral heating curve whereby on the basis of this or another progression of the combustion characterizing the combustion or the combustion curve at least one separate feature as a third value or possibly several separate features as further values are determined which facilitate the subdivision of the combustion curve into two sub-curves, whereby for example one of the sub-curves, in particular the first sub-curve in terms of time, is assigned to a normal combustion for operating the internal combustion engine, while the second sub-curve, in particular the later of the two sub-curves in time, is assigned to a special combustion which is carried out during said special operating states.

It is thus possible to define a respective mass conversion, in particular an energy release, in the combustions (main combustion, special combustion).

If the feature(s) characterizing the two combustions is/are used as an input value in a closed regulating circuit and/or in an interweaving element of two combined regulating circuits, a stabilization of the whole combustion through a corresponding multi-value regulation of an injection position of the fuel injections into the combustion chamber to be carried out can be achieved in all operating states of the internal combustion engine. Through corresponding coordination, for example in the form of ramps, that is, ramp-like transitions, a continuous regulation of the transitions between the different operating states of the internal combustion engine, thus between operating states wherein a corresponding special combustion is provided and those wherein no special combustion is provided, is possible in a very efficient manner corresponding to needs and without the need for additional characteristic fields or detection devices. This keeps the resources required for carrying out the method low, which goes hand in hand with low costs.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment with reference to the accompanying drawing. The features and feature combinations mentioned above and the features and feature combinations mentioned below in the description of the drawing and/or shown only in the drawing can be used not only in the respectively indicated combination but also in other combinations or alone without going outside of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows an integral heating curve of a combustion in a combustion chamber of an internal combustion engine over a crankshaft angle position thereof, wherein the heating curve represents a value which characterizes an accumulation of the energy released during a combustion in the combustion chamber and whereby on the basis of the heating curve at least one value is determined, by means of which the combustion curve is subdivided into two sub-curves.

The drawing shows a diagram 10 for illustrating a method for operating an internal combustion engine comprising at least one cylinder which allows the internal combustion engine to also be optimally controlled in a so-called special operating state differing from the normal operating state and provide for an optimal transition between a normal operating state and a special operating state.

A normal operating state is for example an operating state, wherein the internal combustion engine serves merely to operate a corresponding motor car. A special operating state is an operating state of the internal combustion engine, wherein for example a regeneration of a particle filter is carried out, which thus means that through corresponding measures within the engine the particle filter is freed from particles, for example soot. This is called filter particle burn-off.

In such a method a first value characterizing the pressure in the combustion chamber is detected by means of a pressure sensor element assigned to the cylinder.

It should be noted at this point that, for the sake of simplicity within the scope of the description of the method merely one cylinder will be described. It is understood that in case of a multi-cylinder internal combustion engine the indications can be applied correspondingly to other cylinders.

On the basis of the first value a second value characterizing a curve of the energy released during a combustion in the cylinder is determined which in case of the diagram 10 is present in the form of a standardized, integral heating curve 16.

A crankshaft angle position of the internal combustion engine in relation to the ignition top dead center is entered on the x axis 12 of diagram 10 in the unit degrees of crankshaft angle [° crankshaft angle], while said heating progression 16 standardized from 0 to 1 is entered on the y axis 14 of the diagram 10.

In the combustion characterized by the integral heating curve 16 or progression of the combustion shown in diagram 10 it is a question of a combustion, wherein a main combustion which is also described as a normal combustion and a post-combustion which is also described as a special combustion are provided, wherein the main combustion serves for operation of the internal combustion engine and is to primarily fulfill the purpose of operating a corresponding motor car.

The special combustion is for example established to fulfill the purpose of burning off deposits in a corresponding exhaust gas purification device such as for example a particle filter.

For the subdivision of the whole combustion curve a third value 18 is determined within the scope of the method described, by means of which the progression of the combustion or the heating curve 16 is subdivided into a first sub-curve 20 and a second sub-curve 22. The first sub-curve 20 which lies in terms of time and also degrees of the crankshaft angle before the second sub-curve 22 is thereby assigned to the main combustion, and the sub-curve 22, later in time, is assigned to said special combustion. An intermediate value 24 and a further intermediate value 26 are determined for further characterization of the sub-curves 20 and 22, by reference to which the two sub-curves 20 and 22 are to be characterized.

As becomes clear by reference to the drawing, the progression of the combustion in the work chamber is thereby optimally divided and the sub-curves 20 and 22 are optimally characterized, which facilitates an efficient and optimal operation of the internal combustion engine, in particular in the presence of special combustions, which special combustion can now be controlled. Furthermore this characterization and subdivision is possible without further sensor elements causing additional costs and also without complicated correction functions and characteristic fields. This keeps the resources and thus the costs for this process and thus for the corresponding internal combustion engine low. If said values or features are used as input values in a closed control circuit or in an interaction of two combined control circuits, a stabilization of the combustion in all operating states of the internal combustion engine can be achieved. Furthermore through corresponding coordination (ramps) a continuous control of transitions between different operating states is possible in a simple and very efficient way.

The method thus allows the special combustion to be used in a targeted way and with low fuel consumption with simultaneous realization of a maximum effect, for example for optimum burn-off of the particle filter.

The method can be used in association with any type of internal combustion engines, that is, for example a gasoline engine, a diesel engine or similar. 

1. A method for operating an internal combustion engine comprising at least one cylinder with a combustion chamber and at least one detection device assigned to the combustion chamber, the method comprising the steps of: determining a first value characterizing a pressure in the combustion chamber, and on the basis of the first value determining at least a second value (16) characterizing a curve of the energy values released during a combustion in the combustion chamber, then on the basis of the second value (16) determining at least a third value (18) by which the progression of the combustion is subdivided into at least two sub-curves (20, 22), and assigning one of the sub-curves (20, 22) to a normal combustion for operation of the internal combustion engine and assigning the other of the sub-curves (20, 22) to a special combustion differing from the normal combustion.
 2. The method according to claim 1, wherein the two sub-curves (20, 22) are characterized respectively by first and second further values (24, 26).
 3. The method according to claim 1, wherein the third value (18) is fed to at least one closed control circuit.
 4. The method according to claim 2, wherein the second further value (26) is fed to at least one closed control circuit.
 5. The method according to claim 1, wherein the first and second further values (24, 26) are fed to at least two combined interacting control circuits.
 6. The method according to claim 5, wherein a stabilization of the combustion is carried out depending on at least one of the third value (18) and the further values (24, 26).
 7. The method according to claim 6, wherein, depending on at least one of the third value (18) and the further values (24, 26), a continuously controlled transition between two different operating states of the internal combustion engine is carried out.
 8. The method according to claim 1, wherein a heating curve, in particular an integral heating curve, is determined as the second value (16).
 9. The method according to claim 1, wherein the special combustion represents one of a regeneration of an exhaust gas purification device, a warm running operation and similar. 